I swear it's snowing!

[bentrw]

Big Island Hawaii.
Found Several dozen of these guys in a small tidal pond surrounded by trees.
Maybe three or four feet deep at most.
Nice layer of mud and leaf fall on the bottom.

Anyway, they looked like giant snowflakes, from 2 to 7 inches across.
Round pulsating skirt under the snowflake-like-top...

Thoughts.

 

[knotical]

The eightfold radial symmetry might place them in the subclass Octocorallia.

edit: scyphozoans also show such symmetry, and seems more likely.

 

[newmanl]

Given your description of where you saw them and their movements, I'd say they appear to be upside down jellies, genus Cassiopea.

Hope that helps.

Lee

 

[ryan115]

I agree...Cassiopea

 

[bentrw]

Thanks! That's the one. Found a few other pics online.